Brandon Caroll writes that when it comes to Ethernet Fabrics, the way we have done this in the past isn't necessarily the best way to do things.

Let's begin with figure 1 where we see a classic ethernet switch topology. In the topology let's assume that we have traffic flowing between Switch A and Switch E. What we know about traditional technology is that for Layer 2 we cannot have a loop. Why? Because loops are bad. Why are they bad? Because of the design of ethernet. So, with that in mind, we are to understand that we have a loop between B, C, and D, and that somehow that loop will be blocked. How so? Spanning Tree Protocol. It doesn't matter if its Rapid, Multiple, or any other flavor. The fact is that it's going to be running and it's going to remove the loop.